An aim in the development of internal combustion engines is that of minimizing fuel consumption. In this connection, too, the supercharging of internal combustion engines is becoming ever more ubiquitous. Supercharging is a suitable means for increasing the power of an internal combustion engine while maintaining an unchanged swept volume, or for reducing the swept volume while maintaining the same power. In any case, supercharging leads to an increase in volumetric power output and an improved power-to-weight ratio. If the swept volume is reduced, it is thus possible, given the same vehicle boundary conditions, to shift the load collective toward higher loads, at which the specific fuel consumption is lower. Supercharging of an internal combustion engine consequently assists in the efforts to minimize fuel consumption, that is to say, to improve the efficiency of the internal combustion engine.
The configuration of the exhaust-gas turbocharging often poses difficulties, wherein it is basically sought to obtain a noticeable performance increase in all engine speed ranges. However, a torque drop is generally observed in the event of a certain engine speed being undershot. Said torque drop is understandable if one takes into consideration that the charge pressure ratio is dependent on the turbine pressure ratio. For example, if the engine speed is reduced, this leads to a smaller exhaust-gas mass flow and therefore to a lower turbine pressure ratio. This has the result that, toward lower engine speeds, the charge pressure ratio and the charge pressure likewise decrease, which equates to a torque drop.
A further approach to a solution for dethrottling an Otto-cycle engine is offered by cylinder deactivation, that is to say the deactivation of individual cylinders in certain load ranges. The efficiency of the Otto-cycle engine in part-load operation can be improved, that is to say increased, by means of a partial deactivation, because the deactivation of one cylinder of a multi-cylinder internal combustion engine increases the load on the other cylinders, which remain in operation, if the engine power remains constant, such that the throttle flap may be opened further in order to introduce a greater air mass into said cylinders, whereby dethrottling of the internal combustion engine is attained overall. During the partial deactivation, the cylinders which are permanently in operation furthermore operate in the region of higher loads, at which the specific fuel consumption is lower. The load collective is shifted toward higher loads.
In the case of diesel engines, the partial deactivation is also intended to prevent the fuel-air mixture from becoming too lean as part of the quality regulation in the event of decreasing load as a result of a reduction of the fuel quantity used.
However, the inventors herein have recognized potential issues with such systems. As one example, the above systems limit an engine load range which cylinders may be deactivated.
In one example, the issues described above may be addressed by a method comprising operating a supercharged auto-ignition internal combustion engine having at least one cylinder head comprising at least two cylinders, each cylinder having at least one outlet opening for discharging exhaust gases to an exhaust-gas discharge system and at least one inlet opening for receiving charge air from an intake system, and where each cylinder further comprises a piston which is movable along a piston longitudinal axis between a bottom dead center BDC and a top dead center TDC; and the intake system further comprising at least one exhaust-gas turbocharger a compressor coupled to a turbine arranged in the exhaust-gas discharge system, adjusting a position of the inlet openings and outlet openings of the cylinders via a valve drive, and deactivating one of the two cylinders during some engine conditions, where the deactivation further includes discharging intake air received by the deactivated cylinder to an operational cylinder through at least one inlet opening of the inlet openings of the deactivated cylinder following a compression stroke of a piston of the deactivated cylinder moving from bottom dead center to top dead center to a flow transfer duct, and where the flow transfer duct direct the discharged charge air to an operational cylinder. In this way, an engine load range in which one or more cylinders of an engine may be deactivated is increased.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.